Order Approval BPM Got Error When Use Variables in SQL

Hi All,

I am using BPM to configure the approval flow of sales orders.

I need to use SQL to got dynamic approver just as I used in other BPMs.

when I use the expression like this:

oraext:query-database(concat('select Listagg( lower(USERNAME), '','' ) approverslist from ( select manager.username from per_users created, DOO_HEADERS_ALL OH, PER_ASSIGNMENT_SUPERVISORS_F ps, per_users manager where created.username=OH.created_by and ps.person_id=created.person_id and ps.MANAGER_ID=manager.person_id and ps.MANAGER_TYPE = ''LINE_MANAGER'' AND sysdate BETWEEN ps.EFFECTIVE_START_DATE AND ps.EFFECTIVE_END_DATE and OH.HEADER_ID=''',